Bonding modes
The Linux bonding driver allows system administrators to set up bonding interfaces with different modes. A bonding mode specifies the policy indicating how bonding slaves are used during network transmission. To achieve the maximum throughput and fault toleration, it is important to choose the proper bonding mode and the corresponding options for the setup.
- mode 0 (balance-rr)
- Round-robin policy. Transmits packets in sequential order from the first available slave through the last. This mode provides load balancing and fault tolerance.
- mode 1 (active-backup)
- Active-backup policy. Establishes that only one slave in the bond is active. A different slave becomes active if, and only if, the active slave fails. The bond's MAC address is externally visible on only one port (network adapter) to avoid confusing the switch. This mode provides fault tolerance. The primary option affects the behavior of this mode.
- mode 2 (balance-xor)
- Transmits based on the selected transmit hash policy, which can be altered via the xmit_hash_policy option. This mode provides load balancing and fault tolerance.
- mode 3 (broadcase)
- Transmits everything on all slave interfaces. This mode provides fault tolerance.
- mode 4 (802.3ad)
- IEEE 802.3ad Dynamic link aggregation policy. Creates aggregation groups that share the same speed and duplex settings. Utilizes all slaves in the active aggregator according to the 802.3ad specification.
- mode 5 (balance-tlb)
- Adaptive transmit load balancing. Establishes channel bonding that does not require any special switch support. The outgoing traffic is distributed according to the current load (computed relative to the speed) on each slave. Incoming traffic is received by the current slave. If the receiving slave fails, another slave takes over the MAC address of the failed receiving slave.
- mode 6 (balance-alb)
- Adaptive load balancing. Includes balance-transmit load balancing plus receive-load balancing for IPv4 traffic, and does not require any special switch support. The receive-load balancing is achieved by ARP negotiation. The bonding driver intercepts the ARP replies sent by the local system on their way out and overwrites the source hardware address with the unique hardware address of one of the slaves in the bond. Thus, different peers use different hardware addresses for the server.
For detailed information about bonding modes, refer to this document: "Linux Ethernet Bonding Driver HOWTO" (https://www.kernel.org/doc/Documentation/networking/bonding.txt).
One bonding interface can only specify one mode. Which mode to choose is dependent on the network topology, requirements for the bonding behaviors, and characteristics of the slave devices. This paper only discusses mode 1 (active-backup) and mode 4 (802.3ad).